This is my assumption from your description without any complete error messages. Please let me know if this is not different from your expectation.
When I compiled the project, I found some error messages as follows.
These warning messages said there are some variables which are set some value but never used in other program parts. These NEVER USED variables are pruned from the program. You can find in the LST files that the function accel_ReadReg() is called but its return value is not used as follows.
30:main.c ****
31:main.c **** XOUT_H = accel_ReadReg(MPU6050_ACCEL_XOUT_H);
55 .loc 1 31 0 discriminator 1
56 0014 3B20 movs r0, #59
57 0016 FFF7FEFF bl accel_ReadReg
58 .LVL3:
32:main.c **** XOUT_L = accel_ReadReg(MPU6050_ACCEL_XOUT_L);
59 .loc 1 32 0 discriminator 1
60 001a 3C20 movs r0, #60
61 001c FFF7FEFF bl accel_ReadReg
62 .LVL4:
33:main.c **** YOUT_H = accel_ReadReg(MPU6050_ACCEL_YOUT_H);
You cannot see the variables because these variables are not assigned to a memory. Yo can use a "Volatile" like
volatile uint8 XOUT_H, XOUT_L, YOUT_H, YOUT_L, ZOUT_H, ZOUT_L; //variables to store the data
to make these variable share a memory area as follows.
30:main.c ****
31:main.c **** XOUT_H = accel_ReadReg(MPU6050_ACCEL_XOUT_H);
56 .loc 1 31 0 discriminator 1
57 0016 3B20 movs r0, #59
58 0018 FFF7FEFF bl accel_ReadReg
59 .LVL3:
60 001c 8DF80700 strb r0, [sp, #7]
32:main.c **** XOUT_L = accel_ReadReg(MPU6050_ACCEL_XOUT_L);
61 .loc 1 32 0 discriminator 1
62 0020 3C20 movs r0, #60
63 0022 FFF7FEFF bl accel_ReadReg
64 .LVL4:
65 0026 8DF80600 strb r0, [sp, #6]
The instruction "strb" is used to store the return value into the local variable on the stack area.
Regards,
Noriaki
